Power supply for electronic apparatus



Oct. 12, 1948. R. PAUST POWER SUPPLY FOR ELECTRONIC APPARATUS 3 Sheets-Sheet 1 Filed Aug. 30, 1945 oo'oooooooo Oct. 12,1948. L. R. PAUST 2,450,985

POWER SUPPLY FOR ELECTRONIC APPARATUS 7 Filed Aug. 50, 1945 Y 3 Sheets-Sheet 2 I a? 4%Hl a. ffiz/ erfign .ZaaarazzceiPazza Oct. 12, 1948. R. PAUST 2,

- POWER SUPPLY FOR ELECTRONIC APPARATUS Filed Aug. 30, 1945 3 Sheets-Sheet 3 five/ 7%? law? 7266 jfazai? Patented Oct. 12, 1948 POWER SUPPLY FOR. ELECTRONIC. APPARATUS Lawrence -Rlzllaust, Chicago,' lll."

ApplicationAugust 30, 1945, Serial No.fi13,5 99

12 Claims.-

This invention relates 'to"'a1-power"supply for" electr'onie apparatus; and "moreparticularly' to means for "energizing "electronic tubes from an alternating current power-source.

One feature of thisinvention is that it provides suitable filament and-plate supplies for electronic tubes with-powerof any'amount desired; i. e., the plate voltages can "be several" times the voltage of the 'ATC. supply source, with attendant maximum:

poweroutput of the tubes.

Another 'feature 'of this' 'inventionis that it transformer.

Still another fea-ture of. the above-"described method of providing filament "and plate supplies forele'ctr'onic tubes isithat the chassis'and'th'e: B return'le'ad are isolatedfronrth'e commercial power supply"circuit; floating as it is sometimes termed? This is particularly important where units are to be connected to "other *units powered from *a difierent wallsocket;for-example; since" heretofore full transformer power supply systems have "been-"the only way to avoid large "circulat ing-currents' "in the chassis gandi'the "necessity, of

isolating connections between the "units.

A 'furtherfeaturepf this invention'is a new andimproved method of energizing"a'pilot lamp: Heretofore pilot lamps have usually "been oper ate'dfrom'a filament winding on'th'e power trans-r former in A. Cxsets 'or connected in series *with'" the-filaments in A? CQ-DL'C. sets or in parallel wit-Ira resistance in series with the filaments: and in-"both these latter cases the "pilot lampghas beenverygreatly' over energized when the set' was first"turned'on:;, Another "method of energizing a pilotlampmequireda tub'e'with acenter tapped filament; not 'very satisfactoryin practice. I am heredi'sclosing a system of energizing a pilot'lamp as a-function of :the plate supply current, either alone' or also *as 'a'function" of th'efi'lament supply, currentf'andso arranging mattersthat the .pilot lamptis never. over-energized-pr caused:to' flash up withundue*brilliance."

2.? 7 Other features and advantages of this invention will be apparent fromith'efollowing;specification and 'the drawings; irr'which:

Figure 1 is a, partial schematic diagram;.of :one system embodying "my invention; an' intercommunicating *system' in'the particular case"illus'-" trated; Figure '2 is'a'circuit'diagram of one of the' intercommuriicating, units shownzinfigure as the uppermost unitof such figure: Figure 31'is a circuit diagram of a portion of theipowersupply circuit showing 'a different .pilbtflamp energize ing arrangement; Figure 4 'is a "circuitfdiagram "of a portion ofithe power :supply :showirig stillian other pilot lamp ,"energizing arrangement; and Figure 5 is acircuitdiagram similartoFigure in so far as the pilot lampjenergizing'jcircuit is concerned but; showing a' fullwave :rectifying' arrangement.

The p'owersupply arrangement whichi am here? disclosing and claiming;- both in-those*aspec.ts which" relate to "energizing," the "electronic tubes and in those aspects 'whichre'late to energizing a pilot-lamp; is'mseful in any-type" of ielectronic apparatus-as radios, public address systems, paging jsystems," electroniccontrols,' etc: merely to' name a few representative"examples,;but::Iam: here illustrating'it inconnection -with an intere communicating system: It will be understood; however, that 'no limitations-"arefto be construed from the specific system" in whichf'I fillustrate it and in-which I willnow describe myinvention;

Referring first moreparticularly-to Figure .1, electronic apparatus incorporating my improvements is illustrated asan: 'intercommurii'catingi 'systemcomprising"threefmaster' units I0, I I and l2, it being understood that-there would normall'yj be a larger number 'of'master units and'generally certain subordinate: units" (comprising; only, speakers and switches and generally calledsubistations) associated with'each'masterunit, Each' of the units'shown'is connected byiitshlocalor' branch cable to a master cable or interconnecting system here identified as I31" Associated with the 1 intercommunicating .units is a general communieating system shown; as comprising an amplifier adapted to. energize speakers l5a and 'I5b"and. another amplifier. I 6 'adaptedto energizerspeakers I'm-d. V

Eachxof therunits 10," H and LIZLcomp'rises, in the particular case illustratecLia dynamic speaker adapted to be operated-selectively by a talk-listen switch having its control .means identified as Illa; i! a and;l2a, sothat'itperfo'rms its speaker function When'communication is being received and performs the function of amicrophone when communication is going out from any particular unit; an amplifier generally comprising 2 or 3 amplifying tubes in cascade; a power supply, as will be hereinafter more fully described; a switching arrangement for selecting the other unit or units of the system with which communication is desired, and any other desired additional controls, as the volume controls here identified as IOb, Nb and I21) and, in the case of the units II and I2, paging switches H and I2c. The controls lllb, llb and I2b are adapted to provide on-ofi switch operation for the units, and manual volume control; and the controls He and 12c enable the units having such controls to actuate the general communicating system.

Inasmuch as the details of this particular intercommunicating system which I have chosen to illustrate as one place where my invention here being claimed may be embodied has been fully described and claimed 2,366,552 of January 2, 1945, it is felt that further detail description of the general apparatus is unnecessary, and I will now direct my description to the circuit diagram comprising Figure 2.

This figure shows a circuit diagram for one of the master units illustrated in Figure l, as the unit I0, without a paging control. The dynamic speaker is shown as adapted to have its actuating or voice coil connected to the primary of transformer 2|, in the position of the switch 22 as shown in solid lines in the drawing, or to the wire 23 in the position of the switch as shown in dotted lines. The first mentioned position of the switch causes the translating device 20 to operate as a microphone, with current variations generated thereby being delivered through an appropriate input network including the transformer 2| to the first amplifying tube 24' which tube may be of tube type No. 12SJ'7, as a representative example. The amplified output of this tube 24 is here shown as delivered through an appropriate resistance coupling arrangement to the second amplifying tube 25, which may be of tube type No. L6, as a representative example. The output of this tube is delivered through an output arrangement including the transformer 26, the switch 21, and the selector switch 28 to the cable connection. The switches 22 and 21 are ganged for operation by the control Illa, the switches being in the position shown in solid lines when the control [0a is as illustrated in Figure 1, with the operator of unit [0 talking; and the switches are moved to the dotted line position by appropriate control operation when the operator of unit [0 desires to listen. Operation of the selector switch 28 enables interconnection of unit In with either of the units II or I2, for example, to effect communicating connections with the translating devices lid. and I 2d thereof. Again it is felt that it would unduly burden the present specification to follow the circuits of this portion of the unit through in detail and to specify resistor and condenser values, etc., as a unit of this type has been fully described in my above-mentioned Patent 2,366,552, to which reference may be made to supplement the present disclosure. Accordingly, this specification will hereafter be concerned only with power supply arrangements for such units, these power supply arrangements including my invention with respect to tube and pilot lamp energization.

Referring now more particularly to the lower half of the sheet comprising Figure 2, connections are suitably made to a conventional source of commercial alternating current, as for example in my Patent of volts, 60 cycles, through the wires 30 and 3|. This circuit may be controlled by an on-off switch of the snap type here identified as 32, this switch being part of the means actuated by the control lllb of the unit 10. An A. C. ground connection is made to this side of the supply line by a condenser 33, which may for example be of .l microfarad capacity. This ground connection is a connection to the chassis of the unit and to B, in the particular case illustrated, although it will be understood that this connection may be to B alone if desired. The power supply circuit is connected to the primary 34a of a power transformer 34, the lead 31 being connected directly to one end of this primary through the on-ofi switch 32 and the lead 30 being connected to the other side of the primary through a resistor 35 comprising part of the system for energizing the pilot light 36, the other portion of the means for developing pilot light energizing voltages comprising the resistor 31.

The transformer 34 is of the step-up type, with its secondary 34b preferably having at least 2 and preferably 3 to 4 times the number of turns of the primary. This transformer is here shown arrangement being connected to ground; and

the positive potential, of at least 250 volts and preferably of the order of 350 volts, is delivered through the lead 42 to the plate supply connections for the amplifying tubes 24 and 25.

Heating current for the rectifier and amplifying tube cathodes is supplied by a direct connection to the A. C. supply source, the Word direct being used throughout this specification and claims in the sense that there is no transformer in the connection isolating the heating connections of the tubes from the supply source. Moreover, while the particular tube types mentioned and illustrated are of the type having cathode sleeves with heaters therewithin having the heating connections made thereto, this invention is equally applicable to tubes of the type where the cathode is a hot filament with the heating connections made directly thereto, as for example an amplifying tube of type No. 46 or a rectifier of tube type No. 80, so that when it is said herein that the tubes have cathodes and heating connections therefor it will be understood that this refers to either arrangement. Moreover, when the word cathode is used alone, it will be understood that any electron emitting element is meant, including even the cold cathode of a rectifying tube of type No. 1348, for example.

In the particular circuit shown and being described the tubes are of the type having cathode sleeves and heaters 24a and 25a of the amplifying tubes 24 and 25 are here shown as connected in series with each other and in series with the heater 38a of the rectifying tube 38. Connection from one end of this group of three heaters in series is made through the resistor 43 and the resistors 31 and 35 to the A. C. line 30; and connection from the other end of this series circuit of the three heaters is made through the wire 44 and the snap switch 32 to the other A. C. lead 3|. The value of the resistor 43 would be selected .in #accordance with the proper current for the heaters; and would .have a value of 300 ohms in connection with the particularhodk-up here beingudescribed. Itwill also ibeunderstood that whileathe tubes are all shownas of a'type having heaters carrying thesarne current, .other tubes with greater or lesser heater draw can be used ifa series parallel .arrangement of the circuit is used;

.With the arrangement just described ,it will be noted that there areno filament windings'on the secondaryof the transformer 34, and accordingly I use :a transformer designed only to handle the plate current draw of the two amplifying tubes and of insufficient capacity to also handle fila' ment power requirements. In the particular case illustrated the transformer need only be made large enough to handle about .15 watts, as theplate eurrent draw will only be in the order of 60' miliiamperes for the amplifying section. This enables a verysmall and compact transformerto' be clesigned, with a relatively small diameter coil and a correspondingly small hole through the core, with a light core becauseof the small watt-' age involved. Filament. wind-ingsare usually of quite-heavy wire. and of about two layers each,

so that two filament windings on a secondary yet a 'very s-mall and light tr'ansformercan b used, with its attendant advantages.

flow oniy, resulting in the light flashing up to unduebrilliance due to over voltage 'when'the} switch is first turned on; and-this results inm'uch shorter life of the pilot lights. I have found that a very satisfactory pilot light energization' can be effected-by the arrangement shown, resulting in the'pilot light coming on at proper voltage (without over-energization) immediately upon turning the set on, and yet subsequently maintain ngproper'brilliance during normal operation oftheapparatus when the tubes have warmed up; Ieifect this by making energization of'the pilot light a function, although not necessarilyexclusively, of plate current draw.

yIn' the particular arrangement illustratedin Figure 2, it will be seen that the plate current draw ofthe amplifying tubes 24 and 25 delivered by the rectifying arrangement constitutes a currentdrain which must be supplied by current passing through the resistor 35 and the transformer primary 34a. Accordingly, once the amplifying tubes have heated up and space current has started to flow therethrough there willbe a voltage drop across the resistor 35 which'is afunction of this space current and of the value of this resistor. The filament or heater draw, howevenalso flows through the resistor 35, the circuit'in this case being through the resistor 35, the resistor 3'1, the resistor 43, and the heaters sea, "25a and 24a in series, the heater 24a beinglast inseries in order to minimize hum. Inasmuch as the pilot light 36 is connected across both re-' sisters 35 and 37, itsenergization will'be a func- Ordinarily, in A. C.-D. C. sets, a pilot light is'actuated as a function of the filament currenttion of the voltage drop across both these re sistors. When the switch :32 is first-turned to onv position there will, of course,::.be :no' space current flow through-the amplifying tubes 24' and 25, and accordingly no drop across the resister .35 as a function of this particular power drain; On"the other hand, the heater current draw is initiallyxhigh, the heaters being cold,-

andthere will beta higher than normal heater current flow through resistors 35 and It \is necessary, therefore, .so tolproportion the ratios between the-:resistors' '35 and 31,.and 'theirtotal resistance, that the current drain across the re-- sistors '35 and 37 when. the switch is first turned on'isjust properifor the energization of the pilot light used. Under'these'circumstances there will be hoover-voltage .energization of the pilot light when the switchisfirst turned on. 'As the heaters come up totemperature the heater current draw willbegi-n. to :drop, and there. may be a period of a .few seconds where: the pilot light dimsvery slightly. -:IIowever, in a matter of seconds the cathodes of the amplifying 'tubes12 i and'25 are heated suificientlyjtog-cause space current to flow through these tubes and through the rectifying tube 38 supplying it, sothatthe voltage drop across the. resistor 35 increases, this now being aifunction both -of the plate currentdraw and-of theheaterflcurrent draw. This results in bringing the; energization-of the pilot light' 36 back to,v

proper brilliance-l nt again without over energization and keeps the pilot light operating at the desired ,energization; level thereafterat the normal operationof the apparatus. .Inthe particular circuit shown and with the particular tubesmentioned, the resistor 35 mayhave a value of ohms and the resistor 31 a value of ohms for proper energizationof a 68 volt .15 ampere pilotlight. In any-event, the value oftheresistor;

3l shouldalways-b e at least several times that of the resistortli, as the voltage drop generated in the resistor '35 by the space current-draw ;of the amplifying tub es should only be such as .to

replace the dr.op of heater current after the heaters warm 'up.' l Figure 3 shows arnodified form of. pilot light energizing arrangement wherein the A. 0. power l nes 58 and '51 again energize the primary of a step-up transformer 52 having one side-of its secondary grounded" and, the other side connected to the anode of arectifying tube. 53 adapted to supply space current or plate current to the amplifying tubes of, the apparatus. lightti4 is in this case connected across a pair of resistors T and 56 in'series in the circuit of the primaryof. the transformer, the mid point between these resistors being connected to a resis tor 51 in series with the heaters .of the rectifier and amplifying tubes. This alternative circuit isparticularlydesirable when amplifying tubes.

are usedhavingsuch characteristics that the plate current drainislow, resulting in low primary current asafunction of the plate current draw. Under these conditions the provision of the additional resist-or 56 increases the effect of the plate current drain as an energizing factor for the-pilot light 54} In this particular-circuit all'of the resistance formerly divided between the resistors 35 and 3'! is concentrated in the resistor 55 which may for example have a value of about 50 ohms with the tubes heretofore mentioned; and the resistor't'! takes the place of the resistor 43 in my first modification, and might have a value-of 3'00 ohms. The original heater current draw thiisresultsin the sameinitialvoltage drop The pilot across the resistor 55 as was the case of the initialdrop across the resistors 35 and 31 in my first form; and this is all the initial voltage applied to the pilot light, as no voltage drop is created across resistor 56 until there is plate current draw in the amplifying tubes. By the time this takes place the initially high heater current has dropped in value and the additional energizing effect resulting from plate current draw is the function of the combined resistance of the resistors 55 and 56, so that by choice of the value of the resistor 56 the pilot light can even be made to light up more brilliantly during normal operation of the apparatus than initially. If the amplifier tubes are biased so as to have low plate current draw the resistor 56 in this circuit might well have a value of about 15 ohms.

Figure 4 is a fragmentary portion of another pilot lamp energizing arrangement which makes pilot light energizati'on a function of plate current draw. In this case only the filter section of a power supply system is shown, comprising the choke 60 and condensers BI and 62. In the positive output lead from the filter, providing the B+ current for the amplifying tubes, is inserted a resistor 63, and the pilot light is placed in shunt with this. In this arrangement energization of the pilot light 64 is solely a function of plate current draw, and accordingly the value of resistor 63 must be somewhat higher than in connection with the arrangements previously described, where pilot light energization was a function of plate current draw and heater current draw combined. For the particular tubes and circuit illustrated in Figure 2, for example, and with a 6-8 volt .15 ampere pilot light, the resistor 63 might well have a value of about 100 ohms. While this form is not my preferred arrangement, as the pilot light does not become illuminated immediately upon turning on the switch, but only after there is plate current draw by the amplifying tubes, this arrangement is prefera-ble to those now commonly used in that the pilot light is not subjected to over voltage initial- 1y.

It will be understood, of course, that any of the arrangements previously described may be used with equal advantage where the power pack arrangement is of the full wave rectifying type. Referring now more particularly to Figure 5, the A. C. supply wires 10 and H are shown as energizing the primary of a power transformer 12, the transformer in this case having a centertapped secondary with its center grounded and its outer ends connected to the anodes of a full wave rectifying tube 13, which may be of tube type No. 25Z5, for example. Heater current for the rectifier tube and the amplifying tube is again provided by a direct connection to the A. C. lines or primary side of the transformer, as by the wires 14' and 15. The particular pilot light energizing arrangement illustrated in this case is similar to that shown and described in Figure 3, comprising resistors I6 and 11 in series with the primary of a transformer, the pilot light 18 being connected in shunt with these, and heater current being taken off from the center point between these resistors through an appropriate current limiting resistor 19.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. Electronic apparatus of the character described adapted to be connected to an alternating current power source, including: a tube having at least plate and cathode elements, a plate cathode circuit associated therewith and heating connections for the cathode element; a transformer having electrically separate primary and secondary windings; means for connecting the secondary winding into the plate cathode circuit of said tube; means for connecting the primary winding to said power source; and means for connecting said heating connections directly to said power source.

2. Electronic apparatus of the character described adapted to be connected to an alternating current power source, including: a plurality of amplifying tubes each having at least plate, grid and cathode elements and heating connections for the cathode element; a transformer having electrically separate primary and secondary windings; apparatus for supplying plate voltage for each of said tubes from the secondary winding; means for connecting the primary winding to said power source; and means for connecting the heating connections of all of said tubes directly to said power source.

3. Electronic apparatus of the character described adapted to be connected to an alternating current power source, including: a plurality of amplifying tubes each having at least plate, grid and cathode elements and heating connections for the cathode element; a rectifying tube having at least plate and cathode elements and a plateca'thode circuit associated therewith; a transformer having electrically separate primary and secondary windings; means for connecting the secondary winding into said plate-cathode circuit; means for supplying plate voltage for all of the amplifying tubes by a circuit connection from said rectifying tubes; means for connecting the primary winding to said power source; and means for connecting the heating connections of all of said tubes directly to said power source.

4. Electronic apparatus of the character described adapted to be connected to an alternating current power source, including: a plurality of amplifying tubes each having at least plate, grid and cathode elements and heating connections for the cathode element; a rectifying tube having at least plate and cathode elements and a plate-cathode circuit associated therewith; a transformer having electrically separate primary and secondary windings; means for connecting the secondary winding into said plate-cathode circuit; means for supplying plate voltage for all of the amplifying tubes by a circuit connection from said rectifying tube; means for connecting the primary winding to said power source; and means for connecting the heating connections of all of the tubes having such connections directly to said power source.

5. Electronic apparatus of the character described adapted to be connected to an alternating current power source, including: a plurality of amplifying tubes each having at least plate, grid and cathode elements and heating connections for the cathode element; a transformer having electrically separate primary and secondary windings, said secondary winding having at least double the number of turns of the primary, the transformer being designed to handle the plate power requirements of said amplifying tubes but being of insufficient capacity to also handle the filament power requirements thereof; a supply circuit for supplying plate voltage for each of said tubes from the secondary windings; means for connecting the primary winding to said power source; and means for connecting the heating connections of all of the tubes having such connections directly to said power source.

6. Electronic apparatus of the character described adapted to be connected to an alternating current power source, including: a plurality of amplifying tubes each having at least plate, grid and cathode elements and heating connections for the cathode element; a transformer having a primary winding and a secondary winding having at least double the number of turns of the primary, the transformer being designed to handle the plate power requirements of said amplifying tubes but being of insufilcient capacity to also handle the filament power requirements thereof; means for supplying plate voltage for each of said tubes from the secondary winding; means for connecting the primary winding to said power source; and means for connecting the heating connections of all of the amplifying tubes directly to said power source, this means including a series resistor.

7. Electronic apparatus of the character described adapted to be connected to an alternating current power source, including: a plurality of amplifying tubes each having at least plate, grid and cathode elements and heating connections for the cathode element; a rectifying tube having at least plate and cathode elements, heating connections for the cathode element and a platecathode circuit associated therewith; a transformer having a primary winding and a secondary winding having at least double the number of turns of the primary, the transformer being designed to handle the plate power requirements of said amplifying tubes but being of insufiicient capacity also to handle the filament power requirements thereof; means for connecting the secondary winding into said plate-cathode circuit; means for supplying plate voltage for all of the amplifying tubes by a circuit connection from said rectifying tube; means for connecting the primary winding to said power source; and means for connecting the heating connections of all of said tubes directly to said power source, this means including a series resistor.

8. Electronic apparatus of the character described, including: a tube having at least plate and cathode elements; apparatus providing a plate cathode circuit for said tube; a pilot lamp; a resistor connected in the path of all the space current passing through said tube and in the path of at least a portion of the current used for heating said cathode; and connections between said resistor and said pilot lamp for energizing the latter.

9. Electronic apparatus of the character described, including: a rectifying tube having at least plate and cathode elements; a pilot lamp; 'a circuit for supplying space current for said tube, this circuit including a resistor so connected as to have all of said space current passing therethrough; a circuit for supplying cathode heating current for at least said tube, this circuit including said resistor and another resistor; and connections between resistance means and said pilot lamp for energizing the latter, this resistance means including said first mentioned resistor and at least one other resistor.

10. Electronic apparatus of the character described, including: a rectifying tube having at least plate and cathode elements; a pilot lamp; a circuit for supplying space current for said tube, this circuit including a resistor so connected as to have all of said space current passing therethrough; a circuit for supplying cathode heating current for at least said tube, this circuit including said resistor and another resistor directly in series with the first mentioned resistor; and connections between said two series resistors and said pilot lamp for energizing the latter.

11. Electronic apparatus of the character described adapted to be connected to an alternating current power source, including: a plurality of amplifying tubes each having at least plate, grid and cathode elements and heating connections for the cathode element; a transformer having electrically separate primary and secondary windings; a supply circuit for supplying plate voltage for each of said tubes from the secondary winding; a circuit for connecting the primary winding to said power source, 'said circuit including a resistor; means for connecting the heating connections of said tubes directly to said power source through said resistor; and a pilot lamp connected to said resistor.

'12. Electronic apparatus of the character described adapted to be connected to an alternating current power source, including: a plurality of amplifying tubes each having at least plate, grid and cathode elements and heating connections for the cathode elements; a transformer having electrically separate primary and secondary windings, said secondary winding having at least double the number of turns of the primary, the transformer being designed to handle the plate power requirements of said amplifying tubes-but being of insufiicient capacity to also handle the filament power requirements thereof; a supply circuit for supplying plate voltage for each of said tubes from the secondary winding; a circuit for connectin the primary winding to said power source through a resistor; means for connecting the heating elements of all of the tubes having heating connections directly to said power source, one of these connections being through said resistor; and a pilot lamp connected to said resistor.

LAWRENCE R. PAUST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

